Synthesis, Crystal Structure, Thermal and Explosive Properties of [Cd(SCZ)₃(H₂O)](PA)₂·3H₂O (SCZ = Semicarbazide, PA = Picrate)

The heptacoordinate transition metal coordination compound [Cd(SCZ)₃(H₂O)](PA)₂·3H₂O (1) with the ligand semicarbazide (SCZ) and the counteranion picrate (PA) was synthesized and characterized by elemental analysis and FTIR spectroscopy. Single-crystal X-ray diffraction analysis revealed that 1 crystallizes in the monoclinic space group P21/c. The Cd²⁺ ion is heptacoordinated by three SCZ groups and a water molecule. SCZ presents typical bidentate coordination modes. The thermal decomposition mechanism of 1 was studied by differential scanning calorimetry (DSC), which revealed that complex 1 exhibits three small endothermic and two large exothermic processes. The non-isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa-Doyle's method, respectively. The heat of combustion was measured by oxygen bomb calorimetry. The enthalpy of formation, the critical temperature of thermal explosion, the entropy of activation (ΔS^≠), the enthalpy of activation (ΔH^≠), and the free energy of activation (ΔG^≠) were also calculated. Sensitivity tests revealed that 1 is insensitive to mechanical stimuli.